A machine for the preparation of pharmaceutical products has a containing liner, a dosing chamber for preparing at least one pharmaceutical product accommodated within the containing liner and a pneumatic ventilation device for feeding two air flows through the dosing chamber and through the containing liner, respectively. Operation of the pneumatic ventilation device is selectively controlled so that the containing liner has inside a pressure lower than a pressure existing within the dosing chamber and than a pressure existing in the environment outside the containing liner itself.